1. Field of the Invention
The present invention relates to subsea drilling and production activities. More particularly, the present invention relates to blowout preventers and other devices in which subsea pipe is closed and/or sheared. Additionally, the present invention relates to shape charges for the cutting a pipe.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
In the operation a blowout preventers in deep water operations, is often necessary to shear pipe within the wellbore and the seal the wellbore to protect the environment in emergency situations when an obstruction is in the wellbore. Shear rams in blowout preventers are designed to cut the pipe in emergency situations and allow the bore to be closed so as to secure the well against unintended discharges of hydrocarbons into the environment. Blind shear rams are designed to both shear the pipe and to seal off the wellbore in a single movement.
Generally, in recent years, drill pipe has become larger in diameter, greater and wall thickness, and a higher yield strength. As such, such drill pipe becomes more difficult to shear. In the past, accumulators have been used as a source of power to carry out the shearing. In many circumstances, the accumulator pressure is it not sufficiently available so as to properly carry out the shearing action. The combination of such difficult pipe and inadequate pressures has resulted in the circumstance in which some pipes cannot be sheared.
It is known that the pipe must be sheared when the maximum anticipated pressure in the bore of the blowout preventer is achieved. This pressure can be generally approximately 15,000 p.s.i. This large amount a pressure can actually act against the shear rams so as to further restrict the ability of the shear rams to carry out the necessary shearing of the pipe.
Blowout preventer systems are known to contain the shear rams. These are major pieces of capital equipment that are placed on the ocean floor in order to provide a conduit for the drill pipe and drilling mud while, the same time, providing pressure protection while drilling holes deep into the earth. The typical blowout preventer has an 18¾ inch bore and operates at working pressures of between 10,000 and 15,000 p.s.i. The blowout preventer is often divided into a lower blowout preventer stack and a lower marine riser package. The lower blowout preventer stack includes a connector for connecting to the wellhead and contains several individual ram-type blowout preventer assemblies which close on various pipe sizes and will close on an open hole through the use of blind rams. The lower marine riser package typically includes a connector at its base for connecting to the top of the lower blowout preventer stack. This contains a single annular preventer for closing any piece of pipe or to close off the open hole. The purpose of the separation between the lower preventer stack and the lower marine riser package is that the annular blowout preventer on the lower marine riser package is the most preferred pressure control assembly. When it experiences a failure or is worn out, it can be released and retrieved to the surface for servicing while the lower blowout preventer stack maintains pressure competency at the wellhead.
Blowout preventers are operated or closed in response to a signal from the surface to a control valve which directs fluid stored in the accumulator bottles to operating cylinders on the blowout preventer. These pressure regulators are set to require a large supply of fluid. Any number of events can prevent the sequence from occurring, such as the failure of the control signals to send the signal, the failure in the connecting lines from the surface, the failure of the valves to close, or the absence of fluid stored under pressure.
When there is a complete failure, it is necessary to have an emergency operation the multiple components in the subsea blowout preventer. A single component, i.e. the blind shear rams can immediately secure an uncontrolled flow of oil or gas from the well. A flat faced gate from each side will meet at the middle in order to seal off the bore. If the pipe is in the bore at the time, it will simply shear the pipe in half and then seal. The blind shear ram is the ultimate safety device, but it must operate. Unfortunately, such rams are not always effective in shearing every type of pipe and are usually limited to the shearing of smaller drill pipe.
High-strength material can adversely affect the ability of such blind shear rams to carry out their intended operation. In other circumstances, there will be other items such as drills, collars, and other items located within the drill pipe. These blind shear rams are often ineffective in cutting through such structures. As such, if such items are positioned in the area of the blind shear rams, there may be a failure in the ultimate final safety mechanism associated with the blowout preventer. As such, need has developed so as to provide further redundancy in connection with the prevention of blowouts.
In the past, various patents have issued relating to devices for the shearing of such pipes. U.S. Pat. No. 3,561,526, issued on Feb. 9, 1971 to Williams, Jr. et al., describes a pipe shearing ram assembly for blowout preventers. This pipe shearing ram assembly has a knife blade that is carried by each of a pair of rams of the ram assembly. The knife blades overlap when the rams are closed with the cutting edge of one knife blade passing just below the cutting edge of the other knife blade to shear a pipe string extending through the preventer. Each knife blade engages a seal member on the other ram. When the rams are closed, they form two vertically spaced seals between the engaging faces of the rams.
U.S. Pat. No. 4,132,267, issued on Jan. 2, 1979 the M. R. Jones, discloses a pipe shearing ram assembly for a blowout preventer having a pair of opposed shear blades. A means is provided for moving the shear blades across the pipe opening. A shoulder on one ram is spaced below the shearing plane of the blades. A face seal is mounted in a recess above the shoulder and below the shearing plane. The leading face of the lower blade coacts with the shoulder to bend a sheared pipe section remaining in its path on the shoulder so that there is no pipe or debris between the leading face and the face seal.
U.S. Pat. No. 5,173,770, issued on Jan. 16, 2001 to C. D. Morrill, provides a shear ram for a ram-type blowout preventer. This ram assembly is positioned in opposed cavities in the body of a blowout preventer. The ram assembly includes a first ram and a second ram. The first and second rams are movable in the cavities along a central guideway axis and between an open position to permit passage of a tubular member through the bore and a closed position to shear the tubular member. First and second shear members are mounted on the first and second rams. Each shear member has a pair of shearing portions disposed on opposite sides of a blade axis. The cutting edges are arranged to shear the tubular member.
U.S. Pat. No. 5,244,336, issued on Jun. 12, 2001 to A. J. Cachich, teaches double shearing rams for blowout preventers. The double shearing rams include an upper shear ram and a mating lower shear ram. The upper shear ram includes an upper cutting blade and a lower guide blade vertically spaced to form a cavity therebetween. The cavity is sized to receive the cutting blade of the lower ram in close fitting engagement when the rams are closed. The upper shear ram has a primary cutting-edge formed on its leading edge and a secondary edge vertically and axially displaced from the primary cutting edge.
U.S. Pat. No. 7,234,530, issued on Jun. 26, 2007 the D. D. Gass, shows a ram-type blowout preventer that includes a body, a first ram block positioned within the body and having a first shearing element and a first sealing element, and a second ram block positioned within the body and opposing the first ram block. The second ram block has a second shearing element and a second sealing element. The blowout preventer includes a load intensifying member coupled to the first ram block in which the first ram block in the second ram blocker is configured to close together upon activation of the blowout preventer.
U.S. Pat. No. 8,443,880, issued on May 21, 2013 to D. Jahnke, describes a blowout preventer having shearing blades. The blowout preventer has a ram with a shear blade for the purpose of shearing a tubular member disposed in the blowout preventer. The profile of the shear blade includes a stress concentrator and centering shaped surface. The stress concentrator and the centering shaped surface can be laterally offset from a centerline of ram travel and on opposite sides of the centerline. An opposing second shear blade can have a mirror image of the shear blade profile with the stressful concentrator and the centering shaped surface reversed to the orientation of the first shear blade.
U.S. Pat. No. 8,448,915, issued on May 28, 2013 to B. F. Baugh, discloses a method of providing a motive force for the rams of a blowout preventer as a function of a desired pressure differential across one or more pistons on the blowout preventer when the desired pressure differential is higher than the gauge pressure of the accumulators that supply the pressure. One or more pistons are connected to the rams. The pistons provide a first pressure from accumulators to the distal side of the pistons.
U.S. Pat. No. 8,567,490, issued on Oct. 29, 2013 to D. W. Van Winkle, provides a shear seal blowout preventer that has a knife edge at the shearing edge. The knife edge is inclined to minimize the cutting force required and to leave a clean cut. The knife edge is presented in an opening of the ram.
It is an object of the present invention to provide an apparatus for the shearing of pipe that is effectively able to cut through any thickness of pipe and any materials that may lie within the interior of the pipe.
It is another object of the present invention to provide an apparatus for the shearing of pipe that is able to cut the pipe immediately.
It is another object of the present invention to provide an apparatus for the shearing of pipe that can be used in conjunction with a mudline closure device or in conjunction with a blowout preventer.
It is still further object of the present invention to provide an apparatus for the shearing of pipe that provides redundancy to the shearing rams associated with the blowout preventer.
It still further object of the present invention to provide an apparatus for the shearing of pipe that is easy to implement, easy to use, and relatively inexpensive.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.